Process and structure for repairing defect of liquid crystal display

ABSTRACT

A process for repairing defects applied in producing a liquid crystal display, wherein the liquid crystal display includes a pixel array formed by a plurality of scanning lines crossing with a plurality of data lines. The process includes steps of providing an essential repair line located on one side of the pixel array, welding a first intersection point of a defecting data line and the essential repair line and a second intersection point of a normal data line adjacent to the defecting data line and the essential repair line by a first laser to achieve electrical connection, and cutting a first breaking point and a second breaking point of the essential repair line by a second laser to achieve a broken circuit, wherein the first and second intersection points are located two sides of a line segment constructed by the first and second intersection points respectively.

FIELD OF THE INVENTION

The present invention relates to a process and a structure for repairingdefects, and more particularly to a process and a structure forrepairing defects of a thin film transistor liquid crystal display(TFTLCD).

BACKGROUND OF THE INVENTION

Along with the producing technology development, the liquid crystaldisplay has been become a widely used display device. The workingprinciple of the liquid crystal display is based on the phenomenon thatthe alignment condition of liquid crystal molecules is changed byapplying an electrical field to change the path of light passing throughthe liquid crystal molecules and the display effect of changing in lightand shade is further achieved.

FIG. 1 is a diagram illustrating a unit circuit block of a thin filmtransistor liquid crystal display according to the prior art. The thinfilm transistor 11 is controlled by the voltage Vs of scanning line forswitching the statuses of “on” and “off”. The voltage Vd of the dataline is applied to a liquid crystal 12 located between a pixel electrode131 and a common electrode 132 for changing the alignment condition ofthe liquid crystal 12 and further controlling the light penetratingdegree of the liquid crystal molecules 12. Thus, the emissive intensityfrom a light source 14 at the back of the liquid crystal display willoccur change while the light reaches to the eyes of a user for achievingthe display effect of the changing in light and shade. The storagecapacitance 15 is used for reinforcing the device characteristics.

The thin film transistor liquid crystal display is formed by producing alot of arrays constructed by the unit circuit as shown in FIG. 1 on adisplay panel. However, some defects in the data or scanning lines arepossible to occur by mistake or through carelessness. For ruling out thedefects, a plurality of annular repair lines around an array areestablished in the layout of the current thin film transistor liquidcrystal display. FIG. 2 is a top view illustrating a structure having aplurality of annular repair lines around the array of the thin filmtransistor liquid crystal display according to the prior art. As shownin FIG. 2, the array 21 has five annular repair lines 201, 202, 203, 204and 205 therearound. When a data line 22 of the array 21 has a breakingpoint occurred, the regions 2011 and 2012 are welded and the regions2013 and 2014 are cut by laser for achieving the repairing effect.

In addition, FIG. 4 is a schematic view illustrating a repair structurefor a liquid crystal display according to a prior art. When a defect isdiscovered, a insulation layer 43 between a first metal layer 41 and asecond metal layer 42 is needed to be destroyed by a laser.Subsequently, the first metal layer 41 is burned to melt, and the firstmetal layer 41 is welded with the second metal layer 42 to accomplishthe repair.

Because the melting point of aluminum is in the range from about 550° C.to 660° C., aluminum is beneficial to the performance of welding. Thefirst metal layer 41 is usually made of aluminum. However, due to thelow melting point of aluminum, aluminum is easily splashed around whenthe welding is performed by the laser. Furthermore, a short circuit, abroken circuit, or a Schottky contact is happened to a contact point.

Thus, using the annular repair lines for repairing the defects accordingto the prior art has the following disadvantages:

(1) The signal transmission line is too long after being repaired, so aserious problem of RC time delay is easy to occur;

(2) A large area of panel is required to move for performing therepairing action, so the production efficiency will be decreased; and

(3) The structure of the repair lines according to the prior artoccupies much area of panel, which decreases the utility rate of glasssubstrates.

(4) The structure of the repair lines according to the prior art easilycauses a short circuit, a broken circuit, or a Schottky contact in acontact point.

Therefore, the purpose of the present invention is to develop a methodto deal with the above situations encountered in the prior art.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to propose a processfor repairing defects of the liquid crystal display to efficientlyshortening a signal transmission line.

It is therefore another object of the present invention to propose aprocess for repairing defects of the liquid crystal display to reducethe RC time delay phenomenon.

It is therefore an additional object of the present invention to proposea process for repairing defects of the liquid crystal display to reducethe moving distance of the laser during repairing.

It is therefore an additional object of the present invention to proposea process for repairing defects of the liquid crystal display to reducethe occupied area of the repair line for efficiently increasing theutility rate of glass substrate in the liquid crystal display.

According to the present invention, there is proposed a process forrepairing defects applied in producing a liquid crystal display, whereinthe liquid crystal display includes a pixel array formed by a pluralityof scanning lines crossing with a plurality of data lines. The processincludes steps of (a) providing an essential repair line located on oneside of the pixel array, (b) welding a first intersection point of adefecting line and the essential repair line and a second intersectionpoint of a normal line adjacent to the defecting line and the essentialrepair line by a first laser to achieve electrical connection, and (c)cutting a first breaking point and a second breaking point of theessential repair line by a second laser to achieve a broken circuit,wherein the first and second intersection points are located two sidesof a line segment constructed by the first and second intersectionpoints respectively.

Preferably, both the defecting line and the normal line are data lines.Certainly, both the defecting line and the normal line can be scanninglines.

Preferably, the first laser has a wavelength of 1064 nm and the secondlaser has a wavelength of 532 nm.

Preferably, the essential repair line includes a first metal layer, asecond metal layer, an insulation layer disposed between the first metallayer and the second metal layer, and a coating layer covering the firstmetal layer and made of a material having a melting point higher thanthat of the first metal layer for avoiding a splash formed by the firstmetal layer in a melting state when the insulation layer is destroyedand the first metal layer is welded by the first laser.

Preferably, the first metal layer is made of aluminum and the coatinglayer is made of indium tin oxide.

Preferably, the second layer is made of chromium, molybdenum, tungstenmolybdate or a combination thereof.

Preferably, the insulation layer is made of silicon nitride (SiN_(x)).

According to the present invention, there is proposed a linear structureof repairing defects applied in producing a liquid crystal display,wherein the liquid crystal display includes a pixel array formed by aplurality of scanning lines crossing with a plurality of data lines. Thelinear structure includes an essential repair line located on one sideof the pixel array and used for intersecting with a defecting line toresult in a first intersection point and with a normal line adjacent tothe defecting line to result in a second intersection point, wherein thefirst and second intersection points are treated by a first laser toachieve electrical connection, and having a first breaking point and asecond breaking point thereof cut by a second laser to achieve a brokencircuit, wherein the first and second intersection points are locatedtwo sides of a line segment constructed by the first and secondintersection points respectively.

Preferably, both the defecting line and the normal line are data lines.Certainly, both the defecting line and the normal line can be scanninglines.

Preferably, the first laser has a wavelength of 1064 nm and the secondlaser has a wavelength of 532 nm.

Preferably, the essential repair line includes a first metal layer, asecond metal layer, an insulation layer disposed between the first metallayer and the second metal layer, and a coating layer covering the firstmetal layer and made of a material having a melting point higher thanthat of the first metal layer for avoiding a splash formed by the firstmetal layer in a melting state when the insulation layer is destroyedand the first metal layer is welded by the first laser.

Preferably, the first metal layer is made of aluminum and the coatinglayer is made of indium tin oxide.

Preferably, the second layer is made of chromium, molybdenum, tungstenmolybdate or a combination thereof.

Preferably, the insulation layer is made of silicon nitride (SiN_(x)).

According to the present invention, there is proposed a repair structureused in a liquid crystal display for being welded by a laser. The repairstructure includes a first metal layer, a second metal layer, aninsulation layer disposed between the first metal layer and the secondmetal layer, and a coating layer covering the first metal layer and madeof a material having a melting point higher than that of the first metallayer for avoiding a splash formed by the first metal layer in a meltingstate when the insulation layer is destroyed and the first metal layeris welded by the laser.

Preferably, the first metal layer is made of aluminum and the coatinglayer is made of indium tin oxide.

Preferably, the second layer is made of chromium, molybdenum, tungstenmolybdate or a combination thereof.

Preferably, the insulation layer is made of silicon nitride (SiN_(x)).

Preferably, the repair structure is an essential repair line forrepairing defects in producing a liquid crystal display including apixel array formed by a plurality of scanning lines crossing with aplurality of data lines. Preferably, the essential repair line islocated on one side of the pixel array and used for intersecting with adefecting line to result in a first intersection point and with a normalline adjacent to the defecting line to result in a second intersectionpoint, wherein the first and second intersection points are treated bythe laser to repair the defects. Preferably, both the defecting line andthe normal line are data lines. Preferably, both the defecting line andthe normal line are scanning lines.

The present invention may best be understood through the followingdescription with reference to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a unit circuit block of a thin filmtransistor liquid crystal display (TFTLCD) according to the prior art;

FIG. 2 is a top view illustrating a structure having a plurality ofannular repair lines around an array of the thin film transistor liquidcrystal display according to the prior art;

FIG. 3A is a diagram illustrating a layout structure according to apreferred embodiment of the present invention;

FIG. 3B is a diagram illustrating a portion of the layout structureaccording to the preferred embodiment of the present invention;

FIG. 4 is a schematic view illustrating a repair structure according toa prior art; and

FIG. 5 is a schematic view illustrating a repair structure according toa preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 3A, a rectangle pixel array 30 of the liquid crystaldisplay has a plurality of scanning lines (not shown) and a plurality ofdata lines (not shown). The present invention provides a repair line311, 312 located outside of the rectangle pixel array 30, e.g. at oneend of the scanning lines or the data lines, for achieving the structureof repairing defects.

During the typical production of the thin film transistor liquid crystaldisplay, generally the scanning lines are finished by the firstphotolithography and etching process. However, the data lines arefinished by the third or fourth photolithography and etching process.Thus, the defect probability of the scanning line is lower than that ofthe data line. In addition, if a defect occurred in the scanning line,the scanning line can be re-worked immediately because the process isearlier process.

The present invention provides a process for repairing defects of a thinfilm transistor liquid crystal display. Referring to FIG. 3B, adefecting data line 32 is occurred in a portion of layout structure. Theprocess for repairing the defect data line 32 is performed by welding afirst intersection point 341 of the defecting data line 32 and therepair line 312 and a second intersection point 342 of a normal dataline 33 adjacent to the defecting data line 32 and the repair line 312by a first laser to achieve electrical connection, and then cutting afirst breaking point 343 and a second breaking point 344 of the repairline 312 by a second laser to achieve a broken circuit. As shown in FIG.3B, the first and second intersection points 343 and 344 are located twosides of a line segment constructed by the first and second intersectionpoints 341 and 342 respectively. Thus, a signal of the normal data line33 can pass the second intersection point 342 and the first intersectionpoint 341 to repair the defecting data line 32. In addition, thewavelength of the first laser is preferably 1064 nm while the wavelengthof second laser, which requires higher energy, is preferably 532 nm.

The selection of the normal data line 33 adjacent to the defecting dataline 32 is in accordance with the transmission of the driving system.Generally, for a set of three primary colors (RGB) and even/oddtransmission, the normal data line 33 having the same primary color andthe same even (or odd) is preferably selected as shown in FIG. 3B.

Moreover, the process for repairing a defecting scanning line is thesame as that for repairing the defecting data line. Therefore, it won'tbe described again.

In addition, the repair line includes a second metal layer 52, aninsulation layer 53, and a first metal layer 51 formed in sequence on aglass substrate 50 as shown in FIG. 5. A coating layer 54 is made of amaterial having a higher melting point than the first metal layer 51.Furthermore, a liquid crystal 55 and a color filter 56 are disposedbetween the second metal layer 52 and a second glass substrate 57.

When a defect of the LCD is found, the insulation layer 53 is destroyedby a laser and the first metal layer 51 is burned to melt. Subsequently,the first metal layer 51 is welded with the second metal layer 52 toaccomplish the repair. In the meantime, the coating layer 54 could avoida splash formed by the first metal layer 51 which is in a melting state.Furthermore, the undesirable contact such as a short circuit, a brokencircuit, or a Schottky contact could be avoided.

According to the present invention, the first metal layer 51 is made ofaluminum, and the insulation layer 53 is made of silicon nitride(SiN_(x)). In addition, the coating layer 54 is made of indium tinoxide. The melting point of indium tin oxide is about 1000° C. whichmuch higher than the melting point of aluminum (550˜660° C.), so thecoating layer 54 is preferably made of indium tin oxide.

According to the present invention, the second metal layer 52 is made ofa conducting material having a melting point much higher than 1000° C.selected from a group consisting of chromium, molybdenum, tungstenmolybdate and the combination thereof.

The wavelength of the laser is preferred 1064 nanometer. The intensityof the laser is preferred low energy. Certainly, the repair structurecould be inverted, so the second glass substrate 57 is in the bottom andthe first glass substrate 50 is on the top. The laser passes from thefirst glass substrate 50 inward to the repair structure.

According to the present invention, the coating layer 54 coating on thefirst metal layer 51 could effectively avoid the splashing. Furthermore,the proper wavelength and intensity of the laser could make a good ohmiccontact between the first metal layer 51 and the second metal layer 52.

In sum, the present invention discloses a process for repairing thedefect occurred in the data or scanning lines. Furthermore, the presentinvention provides the following advantages:

(1) Comparing with the prior art, the signal transmission line will beefficiently shortened after finishing repairing according to the presentinvention. Thus, the present invention can decrease the RC time delayphenomenon.

(2) The repair line according to the present invention can be used forrepairing multiple defecting lines. Furthermore, a large area of panelis not necessary to move for performing the repairing action. Therefore,the production efficiency will be increased.

(3) The structure of the repair line does not occupy too much area, sothe utility rate of glass substrate in the liquid crystal display can beefficiently increased.

While the invention has been described in terms of what are presentlyconsidered to be the most practical and preferred embodiments, it is tobe understood that the invention need not to be limited to the disclosedembodiment. On the contrary, it is intended to cover variousmodifications and similar arrangements included within the spirit andscope of the appended claims which are to be accorded with the broadestinterpretation so as to encompass all such modifications and similarstructures.

1. A process for repairing defects applied in producing a liquid crystaldisplay, wherein said liquid crystal display comprises a pixel arrayformed by a plurality of scanning lines crossing with a plurality ofdata lines, comprising steps of: (a) providing an essential repair linelocated on one side of said pixel array; (b) welding a firstintersection point of a defecting line and said essential repair lineand a second intersection point of a normal line adjacent to saiddefecting line and said essential repair line by a first laser toachieve electrical connection; and (c) cutting a first breaking pointand a second breaking point of said essential repair line by a secondlaser to achieve a broken circuit, wherein said first and secondintersection points are located two sides of a line segment constructedby said first and second intersection points respectively.
 2. Theprocess according to claim 1, wherein both said defecting line and saidnormal line are data lines.
 3. The process according to claim 1, whereinboth said defecting line and said normal line are scanning lines.
 4. Theprocess according to claim 1, wherein said first laser has a wavelengthof 1064 nm and said second laser has a wavelength of 532 nm.
 5. Theprocess according to claim 1, wherein said essential repair linecomprises: a first metal layer; a second metal layer; an insulationlayer disposed between said first metal layer and said second metallayer; and a coating layer covering said first metal layer and made of amaterial having a melting point higher than that of said first metallayer for avoiding a splash formed by said first metal layer in amelting state when said insulation layer is destroyed and said firstmetal layer is welded by said first laser.
 6. The process according toclaim 5, wherein said first metal layer is made of aluminum.
 7. Theprocess according to claim 5, wherein said coating layer is made ofindium tin oxide.
 8. The process according to claim 5, wherein saidsecond layer is made of a material selected from a group consisting ofchromium, molybdenum, tungsten molybdate and a combination thereof. 9.The process according to claim 5, wherein said insulation layer is madeof silicon nitride (SiN_(x)).